1. Field of the Invention
The present invention relates to systems and methods for protecting vehicle occupants from injury. More specifically, the present invention relates to a side impact airbag with two chambers that can be inflated to different pressures.
2. Description of Related Art
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the expulsion of rapidly expanding gases from an inflator. The expanding gases fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield.
Side impact airbags such as inflatable curtains and seat mounted airbags have also been developed in response to the need for protection from impacts in a lateral direction, or against the side of the vehicle. Other airbags such as knee bolsters and overhead airbags also operate to protect various part of the body from collision.
It has been discovered that various parts of the body require different levels of impact protection. For example, a seat mounted airbag may inflate beside an occupant of a vehicle seat to protect the pelvis and thorax of the occupant against lateral impact. The weight of the occupant may generally tend to slide with the pelvis; hence, it may be beneficial for the pelvic portion of the seat mounted airbag to inflate stiffly to provide comparatively firm protection. By contrast, the thorax is more sensitive and generally carries less mass, and thus should preferably be more softly cushioned during impact to avoid injury due to contact with the airbag. Such differing impact protection levels are reflected in new automotive safety tests, such as the IIHS test.
Unfortunately, many known airbags, including seat mounted side impact airbags, are only able to inflate to one comparatively uniform pressure level. Hence, a part of the occupant's body may be subject to impact protection that is either too rigid or too soft. Of the known airbag systems designed to provide multiple pressures within a single cushion, many have a number of inherent disadvantages.
More precisely, some such airbag systems have inflators that are somewhat difficult to install in the airbag cushion. Some known systems utilize inflators that are somewhat inflexible in their positioning in the cushion or in the vehicle, and thus cannot readily be used for different airbag configurations. Some such airbag systems use inflators in a manner that provides a strongly directional gas jetting force, thereby requiring strengthened inflator mounting hardware and/or additional safeguards to prevent unintentional deployment. Furthermore, some such airbag systems require the use of snorkels or other comparatively expensive hardware to distribute the gas within the cushion. Yet further, many such systems do not permit easy adaptation of the ratio of gas that flows into the various portions of the cushion, and are thus difficult to adapt for use in multiple vehicle configurations.